My guess would be that's just their login, but their email would not have their location sub-domain (I've never seen a sub-domain in e-mail, well actually not true, people with domain + country TLDs all have it, e.g. clarkson@bbc.co.uk).
Of course moving locations/departments would mean getting a new login which is all sorts of problematic.
There’s no reason to do that, though. You can set your MX record to whatever you want for your domain. Why would you set yourself up to have to change your email? Not to mention advertising that your email is on a raspberry pi. Somebody will probably come along and DDOS that thing just for fun.
Of course moving locations/departments would mean getting a new login which is all sorts of problematic.